docs: def _known_stale(self):
          """
          The commit is known to be from a file (and therefore stale) if a
          SHA is supplied by git archive and doesn't match the parsed commit.
          """
          if self._output_from_file() is None:
              commit = None
          else:
              commit = self.commit
  
          known_stale = (self.archive_commit is not None
                         and not self.archive_commit.startswith('$Format')
                         and self.archive_commit != commit)
          if known_stale: self._commit_count = None
          return known_stale